The invention relates to a suction cleaner, more specifically to a suction cleaner which filters entrained dust out of the cleaner's suction airflow by using a dust collection bag in which the dust is retained for disposal. The cleaner described hereafter is of the so-called drum or canister type, but it will be appreciated that the principles of the invention will be applicable to cleaners whose shape differs from that described.
In suction cleaners with dust collection bags, there is a suction creating means, usually an electric motor connected to drive a fan, which transfers air from inside the suction cleaner, discharging through vents to the outside. The suction creating means is in fluid communication with the exterior of a dust collection bag, which has porous walls designed to trap dust but allow airflow therethrough. The interior of the bag is in fluid communication with an inlet which in the case of an “upright” type of cleaner is a cleaning head part of the cleaner's body, or possibly a hose, or in the case of a drum or canister type of cleaner is a suction hose, which the user directs to the area requiring cleaning. The flow created takes dust-filled air through the collection bag wherein the dust is retained, and the resultant clean air, filtered by the bag, flows to the suction creating means and thence to the outside of the cleaner.
It will be appreciated that the term “dust” is used herein as a general term to cover all of the matter that a suction cleaner would be used to collect, rather than as a literal term referring solely to household dust. For example, the term “dust” will cover hair fibres, loose carpet fibres, food particles, soil particles, wood dust, wood shavings, and any other debris, of a size which may range from microns to millimetres.
In a suction cleaner, it is desirable to have a large dust-carrying capacity, so that it requires emptying less frequently. To address this requirement, a large collection bag could be provided, but this would require a larger volume inside the cleaner and thus create a larger suction cleaner as a whole, requiring more material to manufacture and more storage space.
A favourable solution therefore is to ensure that the bag provided is filled as close as possible to its capacity, referred to herein as a high “fill ratio”, and this is dependent upon the path of the airflow which carries the dust through the bag. To this end, many drum-type suction cleaners have the motor disposed overhead of the bag, because this configuration allows some of the volume above the centreline of the inlet port to be filled. However, as the motor is relatively heavy, this results in the cleaner's having a high centre of gravity, making it less stable. This makes it more likely that the cleaner will fall over in use when being pulled along by the hose, especially when the castors commonly used on such suction cleaners have to climb small level differences, such as passing over a cable on the floor, or a door threshold.
The cable for the motor must be relatively thick, due to the power required by the electric motor, which is generally above 1 kW. In addition, it is desirable to provide a long cable so that the operating range of the cleaner from a power supply socket is increased. These factors result in a heavy cable. Many suction cleaners have the cable storage towards the top of the device for ease of access by the user, but this also results in a high centre of gravity, and instability.